The present invention disclosed herein relates to photodiodes and methods of fabricating the same, and more particularly, to avalanche photodiodes and methods of fabricating the same.
A photodetector is essentially used in an optical communication system as a light-receiving device that receives light and converts the same into an electrical signal. Examples of the photodetector include PIN photodetectors and avalanche photodiodes. In particular, an InGaAs/InP avalanche photodiode used for ultrahigh-speed optical communication operates in a 1.3 μm or 1.5 μm long-wavelength region. What is important in the avalanche photodiode is a technology to form an amplification layer that generates avalanche multiplication for optical signal amplification.
Typically, a p-type indium phosphide layer (p-InP) is formed by diffusion and activation of zinc (Zn) atoms in a device region of an undoped indium phosphide layer (u-InP) to form a p-type conductive layer, and a uniform undoped indium phosphide layer (u-InP) is left to form an amplification layer. An amplification layer of an avalanche photodiode generates avalanche multiplication that affects the device characteristics. Therefore, in order to form an undoped indium phosphide layer (u-InP) with a uniform thickness, it is important to obtain an accurate zinc (Zn) diffusion depth, an interface and a uniform zinc (Zn) diffusion distribution layer.